Are You Confident of the Diagnosis?

What you should be alert for in the history

The clinical history for giant cell fibroblastoma (GCF) includes a slow-growing painless mass that is usually on the trunk or thigh, but has been described in a variety of anatomic locations.

Characteristic findings on physical examination

On physical exam, a nontender dermal or subcutaneous mass fixed to overlying skin is found.

Expected results of diagnostic studies

On histopathologic examination, GCF is an infiltrative, relatively hypocellular mass with ill-defined borders, composed of uniform, bland wavy spindled cells in parallel fascicles, with associated wiry collagen bundles and a hyalinized to myxoid stroma. There are also a variable number of pleomorphic hyperchromatic spindle cells and multinucleated tumor cells.

Sinusoidal or “angiectoid” spaces are characteristic, and are often lined by the giant multinucleated cells, but not endothelium. There is a “honeycomb” pattern of fat infiltration. GCF spares adnexal structures and rarely invades superficial muscle. The tumor is positive for CD34. Cytogenetic and molecular studies show t(17;22)(q22;q13) with a COL1A1-PDGFB fusion gene.

Diagnosis confirmation

The main differential diagnosis is dermatofibrosarcoma protuberans (DFSP). DFSP and GCF are considered to be related or within the same tumor spectrum, and hybrid lesions occur. GCF can recur as DFSP, and vice versa.

DFSP occurs in adults and is hypercellular, with a “cartwheel” or storiform arrangement of tumor cells and no multinucleated cells. DFSP has the same translocation and fusion gene, often with ring chromosome r(17;22), which is not present in GCF.

Who is at Risk for Developing this Disease?

Most cases occur in first decade of life. Reported ages range from 6 months to 62 years. Males are affected more frequently. There are rare reports of occurence at site of trauma.

What is the Cause of the Disease?

Etiology

The etiology of GCF is unknown. It may occur at the site of trauma.

Pathophysiology

GCF is thought to be a fibrohistiocytic neoplasm with benign behavior. The t(17;22)(q22;q13) results in the fusion gene COL1A1-PDGFB, which causes upregulation of a fusion protein. A PDGF-BB homodimer ultimately results, activating the tyrosine kinase receptor PDGFBR, stimulating cell proliferation.

Systemic Implications and Complications

There are negligible systemic implications or complications. GCF locally recurs after incomplete excision; recurrence as DFSP has been reported. No GCF metastases have been reported.

Treatment Options

SURGICAL

Surgical excision is the standard treatment, with wide local excision with up to 3cm margins. Some advocate:

2-3cm margins for patients older than 5 years of age

1cm margins for patients younger than 5 years of age

Mohs micrographic surgery has been described for GCF.

MEDICAL

Imatinib mesylate could be considered in large (surgically difficult), locally advanced, or recurrent cases (as in DFSP), and this is under investigation.

Reported pediatric doses (for DFSP): 400-520mg/m2/day

Reported adult doses (for DFSP): 400mg/day to 400mg twice a day

Optimal Therapeutic Approach for this Disease

Complete excision with up to 3cm margins is standard and curative. Although GCF behaves in a benign fashion, a limited excision with positive margins has up to an 80% recurrence rate.

Mohs micrographic surgery has been reported to be successful (similar to DFSP), but there is a paucity of information specific to GCF in the literature.

Patient Management

Wide local excision with negative margins is curative. Patients with positive margins should have re-excision or be closely followed for local recurrence. Remember, this tumor can recur as DFSP.

Unusual Clinical Scenarios to Consider in Patient Management

This tumor, although most frequently seen in children, can occur in adults and should not be misdiagnosed as a sarcoma, which has therapeutic and prognostic significance.

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